Theory of Constraints (TOC) is new concept of project management. Every project has some constraints. This study explores the constraints to improve the project performance dealing with time constraint with a case of Sankosh-Tipling Road project and Bhimdhunga-Lamidanda Road Project of Dhading District. Questionnaire survey, Project report analysis, Key informant interview and case studies were the methods used for the data collection and content analysis, S-Curve and interim payment assessment were done to process the data. The major constraint among several other constraints in Bhimdhunga-Lamidanda Road project, legal constraint which is restriction of District Coordination Committee (DCC) to collect gravel and boulders from river and quarry sites was found as major constraint in the project. Constraint has affected with time extension for total 309 days with progress of only 34.76% till 13 june, 2017. Thus, this study has assumed that project could be completed within previously proposed deadline if different counter measures which have been suggested with consideration of TOC.